Cannot Receive e-mail from POP3 connector

Hello,

We are running exchange 2003 and using Native Pop3 Connector - http://www.mapilab.com/exchange/pop3_connector/ instead of Microsofts POP3 connector to download e-mail off our external e-mail addresses.  Exchange does not serve as our primary e-mail server.  We use Native POP3 connector because it offers smaller intervals of times between checking the inboxes.

Lately however - our exchange server has been the target of some direct and sneaky spam. masquarading as "Undeliverable"

Seeing as our exchange server doesn't (shouldn't) receive emails directly - but instead get e-mails from our offsite e-mail server via pop3,  I disabled anonymous connections in the default smtp virtual server - and whitelisted our offsite e-mail server.

However - I am not receiving e-mails now.  If I send an e-mail from gmail - or other e-mail server, the Offsite server receives the e-mail, the pop3 connector downloads the e-mail - as it it shortly removed from the offsite server, but the e-mail never shows up in my exchange mailbox.  If I enable anonymous authentication to the default smtp virtual server, then the e-mails show up in my exchange mailbox.

What gives?
kemhofAsked:
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kieran_bCommented:
Alternatively, just block port 25 access to your exchange server in the firewall.

Mapilabs POP3 connector is special in that as Mikkk indicated, it actually sends your server the mail - most POP3 connectors don't, they just drop it in the queue and Exchange processes them.

Kieran
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MikkkCommented:
You can't disable anonymous connections to your SMTP server if your POP connector software is not able to send mails to it via non anonymous connectons.
That is, when you do it, Exchange only allows geting SMTP mails is they are validated with a actyve directory domain user and password.
So, enable anonymous connections (almost all servers has it enabled) or disable it and configure POP Connector to send downloaded mails to Exchange via secure-validated user connection (I supose it will not be able to do it)
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kemhofAuthor Commented:
I did not realize that mapilabs POP3 connector delivered e-mails to the exchange store via SMTP.

I solved the situation by allowing anonymous connections - but restricting  connections to a specific list of IP's that can connect to the SMTP virtual server

Thanks for the info
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